1. Field of the Invention
The present invention relates to a vehicle lamp and more particularly to a vehicle lamp provided with a bracket that projects on a synthetic resin lamp body so that the lamp is mounted on a vehicle body, an adjacent lamp and the like.
2. Prior Art
In one type of vehicle lamp disclosed in, for instance, U.S. Pat. No. 6,257,749, a bracket and a boss are formed on the exterior surface of the lamp body. The bracket projects on the lamp body, that is typically a synthetic resin made, so as to function as a fixation portion that is fixed to a vehicle body, an adjacent lamp, and the like. The boss is provided near the bracket. The boss is used for attaching a replacement bracket thereto so that in case the bracket is damaged the replacement bracket is replaced with such a damaged bracket. The replacement bracket is attached to the boss by screwing a tapping screw into the boss hole.
When, for instance, a vehicle collision occurs but the lamp body remains undamaged and only the bracket is damaged, then the damaged bracket is removed, a replacement bracket is attached to the boss, and thus the undamaged lamp body is mounted back on the vehicle. It is thus unnecessary to replace the entire vehicle lamp.
However, in this prior art vehicle lamp body, the boss hole that is provided in the boss and into which the tapping screw is screwed, is narrow and deep and thus has several problems.
First, the boss hole can be easily clogged with mud, gravel, duet and the like. When the boss hole is thus clogged, then it is difficult to remove the clogged mud, gravel, duet and the like. As a result, it is impossible to sufficiently screw the tapping screw into the boss hole; and the attachment strength of the replacement bracket becomes insufficient.
Second, the boss for attaching the replacement bracket is generally formed after the design of a lamp body is completed, the portions that can be easily damaged are identified through tests using a prototype formed with a metallic mold, and concave portions or pins are formed in the metallic mold according to design changes. However, the process of providing the thin and long pin for forming the boss hole in the metallic mold is troublesome. Thus, a great amount of energy is required to provide the boss that may not be used in the future, and the cost of the vehicle lamp becomes relatively high. In addition, because of the structure of the metallic mold, the positions where the long pin for forming the boss hole can be provided are limited. Therefore, the boss is not always formed at an appropriate position, and a sufficient high attachment strength for the replacement bracket may not be obtained.
Accordingly, the inventors of the present application formed a shallow boss hole that has a bore diameter that gradually increases from the bottom to the open end, and the inventors found that such a shallow boss hole is effective for solving the various problems seen in the prior art structures.
Moreover, the inventors found that when a tapping screw that has a sharp end is screwed into the shallow boss hole, no crack occurs in the boss and the attachment strength of the replacement bracket is not greatly reduced even when whitening due to plastic deformation occurs in the boss.
The present invention is made in view of the above-described problems with the prior art and based on the above-described findings made by the inventors.
Accordingly, an object of the present invention is to provide a vehicle lamp in which a boss hole provided in a boss for attaching a replacement bracket is formed so as to have a small depth, thereby preventing the boss hole from being clogged with water, mud, gravel and the like, eliminating the use of complicated metallic mold for forming a lamp body and reducing the positional restrictions in forming the boss.
The above object is accomplished by a unique structure for a vehicle lamp of the present invention that includes a bracket and a boss, in which the bracket is projects from the exterior surface of a synthetic resin lamp body and functions as a fixation portion to be fixed to a vehicle body, an adjacent lamp, and the like; and the boss is provided in the vicinity of the bracket of the lamp body so as to be used for attaching a replacement bracket thereon that is to be replaced with a damaged bracket, the boss being formed with a boss hole or a recess into which a tapping screw is pressed and screwed, wherein the boss hole or the recess has a small depth, and the bore diameter gradually increases from the bottom toward its open end.
Conceivable shapes of the boss hole include, for example, a conical shape, a truncated conical shape, and a mortar-like shape. Since the depth of the boss hole is small, and the bore diameter of the boss hole gradually increases toward the open end, the boss hole is not easily clogged with mud, gravel, dust, and the like. Also, since a long pin for forming a boss hole does not need to be provided in the metallic mold, positional restrictions in forming the boss are small, and the boss (and boss hole) having a high strength can be formed at an optimal position.
When a tapping screw is installed, the screw is guided by the inner peripheral surface of the boss hole that has a bore diameter which gradually changes (or decrease toward the bottom of the boss hole), and the tip end of the tapping screw is easily aligned with the center of the boss hole. Thus, when the tapping screw having a sharp end is screwed into the thus formed shallow boss hole, the tapping screw is pressed and screwed straight into the boss. Also, no crack would occur in the boss, and the attachment strength of the replacement bracket is not greatly reduced even when whitening due to plastic deformation occurs in the boss.
In the present invention, the boss hole can be in a conical shape.
The conical boss hole is not easily clogged with mud, gravel, dust, and the like. When the tapping screw is inserted into the conical boss hole, the tip end of the tapping screw is guided by the side wall of the boss hole, and the center of the tapping screw is aligned with the center of the boss hole. Moreover, for forming such a boss hole of a conical shape, it is only necessary to form a conical projection in the metallic mold; and such a conical projection can be easily formed by, for example, welding.
More specifically, in the present invention, the ratio H/D is set to be in the range of xc2xc less than H/D  less than {fraction (3/2)} when H is the depth of the boss hole, and D is the bore diameter of the boss hole.
When the ratio H/D is smaller than xc2xc, the tip end of the tapping screw is not efficiently guided into the center of the boss hole. On the other hand, when the ratio H/D is greater than {fraction (3/2)}, then the boss hole is easily clogged with water, gravel, mud, and the like; and also, it is difficult to form a projection (for forming such a boss hole having the H/D ratio that is greater than {fraction (3/2)}) in the metallic mold that is used for molding the lamp body.
Furthermore, in the present invention, a taper angle xcex8 of the inner peripheral surface of the boss hole is set to a value in the range of 20 degrees less than xcex8 less than 60 degrees.
When the taper angle xcex8 of the boss hole inner peripheral surface is smaller than 20 degrees, the boss hole is easily clogged. On the other hand, when the taper angle xcex8 is larger than 60 degrees, then the function to guide the end of the tapping screw into the center of the boss hole deteriorates.
Also, in the present invention, the bracket is formed at its base end with horizontal ribs that stand on the lamp body and extend horizontally, and the replacement bracket is formed with a slit that is engageable with the horizontal rib of the bracket, so that the replacement bracket is attached to the boss with the slit being engaged with the horizontal rib.
When the replacement bracket is attached to the boss formed on the lamp body, the slit of the replacement bracket is brought to engage with the horizontal rib formed on the lamp body. Thus, the portion of the replacement bracket that has the slit supports the lamp weight load; and the lamp weight load imposed on the fixation portion of the replacement bracket that is to be fixed to the boss with the tapping screw is reduced.
In addition, in the present invention, the slit is formed in the replacement bracket so as to be located between the base end portion that is attached to the boss of the lamp body and the front end portion that is fixed to the vehicle body.
In this structure, when the replacement bracket is attached to the boss, the slit of the replacement bracket, which is engaged with the horizontal rib of the lamp body, is between the fixation portion attached to the boss and the fixation portion fixed to the vehicle body. This arrangement reduces further the lamp weight load imposed on the fixation portion of the replacement bracket attached to the boss with the tapping screw. More specifically, the slit of the replacement bracket is provided at a closer position to the fixation portion (the front end portion) that is fixed to the vehicle than to the fixation portion (the base end portion) to be fixed to the boss. Therefore, the lamp weight load imposed on the fixation portion (the base end portion) fixed to the boss is less than the lamp weight load imposed on the slit.